Fuel system



FUEL SYSTEM INVENTOR. Y :Erome 3% B MUM 9 A T TOR E y J B. YORK, JR

Filed Sept. 16, 1965 j; w J m Mm MWQ u @R flx FR I f F\ v\ M33 A/// /A/ Wm g i mm 7 JW? June 4, 1968 United States Patent 3,386,710 FUEL SYSTEM Jerome 11. York, Jr., Royal Oak, Mich assignor to General Motors Corporation, Detroit, Mich, a corporation of Delaware Filed Sept. 16, 1965, Ser. No. 487,801 5 Claims. (Cl. 261-36) This invention relates to fuel systems and is particularly directed to fuel systems utilizing fluid amplifier technology.

Because spark ignition internal cumbustion engines are quite sensitive to the proportions of the air-fuel mixture in the combustion chamber, innumerable systems have been developed in attempts to supply the engine with an air-fuel mixture proper for the various operating conditions. The systems in common use, however, include a venturi located in the air inlet to create a pressure signal which varies with the rate of air flow to the engine; this pressure signal determines the rate at which fuel is delivered to the engine.

Unfortunately however, the venturi signal does not vary linearly with air flow. When utilizing a large venturi to avoid restricting air flow at high air flow rates, the venturi signal is weak at low air flow rates. This weak signal would result in insuihcient fuel delivery to the engine. On the other hand, a small venturi which would provide an adequate fuel metering signal at low air flow rates would also restrict air flow at high air flow rates. For these reasons, a compromise is generally adopted in which a separate idle system provides fuel at the lowest air flow rates, a large venturi and one or two small boost venturi provide a fuel metering signal over the part throttle and Wide-open throttle operating ranges, and offidle discharge ports smooth the transition from the idle system to the venturi metering system as the throttle opens.

Fuel systems have recently been developed which utilize fluid amplifiers to amplify the venturi pressure signal and deliver fuel to the engine at a rate determined by the amplified signal. Such an arrangement makes a complex system unnecessary.

As more extensively discussed in recent literature, Control Engineering of January 1963, for example, a fluid amplifier uses a relatively weak control signal to deflect a fluid jet. Because relatively large deflections in the jet are obtained with weak control signals, a more sensitive control function is obtained by utilizing the deflection of the jet rather than by directly utilizing the control signal.

This invention, directed to such a fluid amplifier controlled fuel system, provides means to vary the rate of flow through the amplifier in response to engine operating conditions. Thus, this invention causes the mixture to be enriched whenever acceleration or maximum power are required of the engine.

In addition, this invention provides means for controlling the gain of a fluid amplifier so that the desired amplification of a control signal such as venturi pressure may be achieved.

The details as well as other objects and advantages of this invention are disclosed in the following description and in the accompanying drawing which illustrates a fuel system carburetor embodying this invention.

Referring to the drawing, a carburetor has an air inlet 12 controlled by a throttle 14 in the customary manner. A venturi 16 provides a restriction within air inlet 12 which reduces the pressure of the air flow therethrough to create a control signal related to the rate of air flow.

A fluid amplifier, indicated generally at It}, has an inlet 20 opening from the carburetor fuel bowl 22 into an interaction region 23. The fuel level within bowl 22 is main- "ice tained at a substantially constant level by a conventional float and inlet valve mechanism 24. Fuel fiow from bowl 22 provides a stream of fuel through amplifier 18 which is issued along a predetermined path Within interaction region 23 and which has a predetermined energy state. The fuel stream is discharged from interaction region 23 through outlets 26 and 28. With the amplifier construction so far described, the proportion of fuel discharged from outlet 26 is determined by the location of the splitter 30.

As air flows through the carburetor inlet 12 and the venturi 16, a pressure drop is produced to create a signal which is transferred through a fuel inlet nozzle 32, a passage 33, and amplifier outlet 26 to amplifier 18. This pressure signal has an energy state much lower than that of the air stream issued from inlet 20 but deflects the fuel stream to change the proportion of fuel discharged through outlet 26. As air flow through the carburetor inlet 12 increases, the pressure in venturi 16 drops further; this reduced pressure sensed through amplifier outlet 26 deflects more of the fuel flow through amplifier 18 to outlet 26.

In addition to the control by venturi pressure, the pressure at a bias port 34 provides a low energy signal which affects fuel flow through amplifier 18. As the pressure at bias port 34 increases, more of the fuel flow from inlet 20 will be deflected to outlet 26. The pressure at bias port 34 is controlled by means to be described below.

An amplifier which operates as described is known as a proportional amplifier since the proportion of fuel discharged through outlet 26 varies with the pressure differential across the fuel stream, i.e., with the pressure differential between bias port 34 and venturi 16.

The rate of fuel flow through inlet 20 is determined by the difference in the pressure on the free surface of the fuel and the pressure in amplifier inlet 26. As described above the pressure in venturi 16 is sensed within amplifier 18 adjacent inlet 20, thereby causing the pressure in inlet 26 to vary with the venturi signal. A passage 36 connects the bowl chamber 22 above the fuel level with venturi 16 to vary the pressure above the fuel level with the venturi signal. Thus, the difference in the pressure on the free surface of the fuel and the pressure in amplifier inlet 20 is held substantially constant so that fuel flows through amplifier 18 at a predetermined rate. Amplifier 18 is constructed so that the fuel flow from inlet 20 is divided and a portion directed through fuel inlet 32 to form an air-fuel mixture suitable for economy operation of the engine.

A restriction 38 in passage 36 prevents a sudden change in the rate of air flow through carburetor air inlet 12 and the concomitant pressure change in venturi 16 from suddenly changing the pressure above the fuel in bowl 22. Therefore, upon a sudden throttle opening and the sudden increase in the air flow rate, the pressure above the fuel will be slowly reduced until it is balanced with venturi pressure. During this period of gradual fuel bowl pressure reduction, the fuel flow through amplifier inlet 20 and thus the fuel flow discharged through amplifier outlet 26 and fuel inlet 32 will temporarily be greater than that which would provide an economy air-fuel mixture. This increased fuel flow provides an enriched mixture to accelerate the engine.

A pressure responsive piston 40 controls a valve 42 to admit air through a restriction 43 to the fuel bowl chamber 22 above the fuel level. Intake manifold vacuum which exists in carburetor inlet 12 below throttle 14 is applied through a passage 44 against piston 40 in opposition to the bias of a spring 46. During normal engine operation, the manifold vacuum will be sufiicient to cause piston 46 to close valve 42. When manifold vacuum reaches a value indicative of the engines requirement for an enriched mixture for maximum power operation,

spring 46 overcomes the vacuum to raise the piston 46 and open valve 42. The air admitted to fuel bowl chamber 22 increases the pressure above the fuel level and causes an increased rate of fuel flow through amplifier inlet 20. As discussed above, this increased rate of fuel flow causes fuel to be delivered through fuel inlet 32 at a rate greater than that which would form an economy air-fuel mixture. The increased fuel flow thus provides an enriched mixture for power operation of the engine.

In some fluid amplifier constructions, the gain of the control signal causes too great a flow of fuel through the outlet 26. In order to reduce the sensitivity or gain of the fluid amplifier, this invention provides means to vary the pressure at bias port 34 in accordance with the control signal. A passage 48 connects bias port 34 to passage 36 and thus to venturi 16. A passage 50 connects passage 48 to atmosphere through a restriction 52. The pressure at bias port 34 is thus related to the venturi pressure signal but has an actual value intermediate the vacuum signal and the atmospheric pressure. Since the delivery of fuel through outlet 26 is determined by the pressure differential between bias port 34 and venturi 16, a reduction in pressure at bias port 34 reduces fuel delivery through outlet 26 and fuel inlet 32. By properly proportioning the restriction 52 within the atmospheric passage 50, the gain of amplifier 18 may be reduced to deliver fuel at any desired rate.

I claim:

1. An internal combustion engine fuel system comprismg a nozzle adapted to discharge fuel for mixture with air,

fluid amplifier means including an interaction region and an inlet port opening into said interaction region,

a source of liquid fuel connected to said inlet port for issuing a liquid fuel stream along a predetermined path within said interaction region, said fuel stream having a certain energy state,

an air inlet for air flow to the engine,

a venturi in said air inlet connected to said interaction region for supplying a pressure signal indicative of the rate of air flow through said air inlet and having an energy state substantially lower than the energy state of the liquid fuel stream and variations of which cause the path of the fuel stream to vary within said interaction region in proportion to the pressure signal variations,

said amplifier means further including outlet means opening from said interaction region for receiving the liquid fuel stream, said outlet means having a pair of outlets and a splitter for dividing the liquid fuel stream between said outlets in accordance with varia tions in the path of the fuel stream and for continuously varying the division of the fuel stream over the range of variations in the path of the fuel stream and for directing an increased flow of fuel to one of said outlets upon a change in the pressure signal indicative of increased air flow through said air inlet,

passage means connecting said nozzle to said one outlet for directing liquid fuel from said one outlet to said nozzle,

and regulating means for controlling the rate of fuel flow through said inlet port to compensate for the variations in pressure within said interaction region caused by the venturi pressure signal.

2. The fuel system of claim 1 wherein said source of fuel comprises a fuel bowl having means for maintaining fuel at a substantially constant level therein and wherein said regulating means comprises a regulating passage extending from said venturi to the top of said fuel bowl 4 whereby the pressure on the free surface of the fuel in said fuel bowl may vary in accordance with the venturi pressure signal.

3. The fuel system of claim 2 wherein said regulating passage includes a restriction for delaying a reduction in the pressure in said fuel bowl to provide an enriched mixture for acceleration.

4. The fuel system of claim 2 which further includes a vent passage opening into the top of said fuel bowl to supply air thereto and vent valve means responsive to an engine demand for an enriched mixture for opening said vent valve means whereby the pressure in said fuel bowl is increased.

5. An internal combustion engine fuel system comprismg a nozzle adapted to discharge fuel for mixture with air,

fluid amplifier means including an interaction region and an inlet port opening into said interaction region,

a source of liquid fuel connected to said inlet port for issuing a liquid fuel stream along a predetermined path within said interaction region, said fuel stream having a certain energy state,

an air inlet for air flow to the engine,

a venturi in said air inlet connected to said interaction region for supplying a pressure signal indicative of the rate of air flow through said air inlet and having an energy state substantially lower than th energy state of the liquid fuel stream and variations of which cause the path of the fuel stream to vary in a certain plane within said interaction region in proportion to the pressure signal variations,

said amplifier means further including outlet means opening from said interaction region for receiving the liquid fuel stream, said outlet means having a pair of outlets and a splitter for dividing the liquid fuel stream between said outlets in accordance with variations in the path of the fuel stream and for continuously varying the division of the fuel stream over the range of variations in the path of the fuel stream and for directing an increased flow of fuel to one of said outlets upon a change in the pressure signal indicative of increased air flow through said air inlet,

passage means connecting said nozzle to said one outlet for directing liquid fuel from said one outlet to said nozzle,

said amplifier means still further including a regulating port opening into said interaction region in said certain plane,

and passage means connecting said venturi to said regulating port for transmitting another pressure signal to said interaction region in opposition to the firstmentioned pressure signal to reduce the variations in the path of the fuel stream caused by the firstmentioned pressure signal.

References Cited UNITED STATES PATENTS 2,675,217 4/1954 Slason 158-36 2,796,243 6/1957 McDufiie 261-72 X 3,001,539 9/1961 Hurvitz 137-815 3,258,023 6/1966 Bowles 137-81.5

FOREIGN PATENTS 1,257,050 2/1961 France.

694,387 7/1953 Great Britain.

289,804 3/ 1954 Switzerland.

HARRY B. THORNTON, Primary Examiner. T. R. MILES, Examiner. 

1. AN INTERNAL COMBUSTION ENGINE FUEL SYSTEM COMPRISING A NOZZLE ADAPTED TO DISCHARGE FUEL FOR MIXTURE WITH AIR, FLUID AMPLIFIER MEANS INCLUDING AN INTERACTION REGION AND AN INLET PORT OPENING INTO SAID INTERACTION REGION, A SOURCE OF LIQUID FUEL CONNECTED TO SAID INLET PORT FOR ISSUING A LIQUID FUEL STREAM ALONG A PREDETERMINED PATH WITHIN SAID INTERACTION REGION, SAID FUEL STREAM HAVING A CERTAIN ENERGY STATE, AN AIR INLET FOR AIR FLOW TO THE ENGINE, A VENTURI IN SAID AIR INLET CONNECTED TO SAID INTERACTION REGION FOR SUPPLYING A PRESSURE SIGNAL INDICATIVE OF THE RATE OF AIR FLOW THROUGH SAID AIR INLET AND HAVING AN ENERGY STATE SUBSTANTIALLY LOWER THAN THE ENERGY STATE OF THE LIQUID FUEL STREAM AND VARIATIONS OF WHICH CAUSE THE PATH OF THE FUEL STREAM TO VARY WITHIN SAID INTERACTION REGION IN PROPORTION TO THE PRESSURE SIGNAL VARIATIONS, SAID AMPLIFIER MEANS FURTHER INCLUDING OUTLET MEANS OPENING FROM SAID INTERACTION REGION FOR RECEIVING THE LIQUID FUEL STREAM, SAID OUTLET MEANS HAVING A PAIR OF OUTLETS AND A SPLITTER FOR DIVIDING THE LIQUID FUEL STREAM BETWEEN SAID OUTLETS IN ACCORDANCE WITH VARIATIONS IN THE PATH OF THE FUEL STREAM AND FOR CONTINUOUSLY VARYING THE DIVISION OF THE FUEL STREAM OVER THE RANGE OF VARIATIONS IN THE PATH OF THE FUEL STREAM AND FOR DIRECTING AN INCREASED FLOW OF FUEL TO ONE OF SAID OUTLETS UPON A CHANGE IN THE PRESSURE SIGNAL INDICATIVE OF INCREASED AIR FLOW THROUG HSAID AIR INLET, PASSAGE MEANS CONNECTING SAID NOZZLE TO SAID ONE OUTLET FOR DIRECTING LIQUID FUEL FROM SAID ONE OUTLET TO SAID NOZZLE, AND REGULATING MEANS FOR CONTROLLING THE RATE OF FUEL FLOW THROUGH SAID INLET PORT TO COMPENSATE FOR THE VARIATIONS IN PRESSURE WITHIN SAID INTERACTION REGION CAUSED BY THE VENTURI PRESSURE SIGNAL. 